text:
I'd like to know the name of this aircraft
I recognize it but can't recall the name, if anyone can tell me that would be great.

Well I MUS say, DANG, I just can't recall what airplane that is--

Google "American WW2 fighters" or something like that and you'll soon know the answer--

@quiet flyer, this is the very definition of low hanging fruit!  Someone will answer this.  And score a few points...  ;)

P.S.  @warwizard57, sorry to tease, but your handle doesn't match the question.  Because if you truly were a war wizard you would know that this is only the most ubiquitous and popular fighter of its era.  Instantantly recognizable by most aviation buffs, it has since dominated air racing, and been reproduced in many smaller scale home built aircraft.

sorry just realized the pun after some thought, my specialty is ground armor in WWII, I don't do well in the aviation department

Is it perhaps specifically one owned by the CAF?

Most postwar Mustangs are "Cavaliers", a postwar civilian retrofit of surplus Mustangs for sale to the sport pilot market in the late 40s/early 50s.  This is why there are so many of them compared to other warbirds where almost all went directly to the scrap yard.  Cavaliers included a back seat in place of the radios and fuel tank in addition to stripping out the weapons, armour and armament.  Because of the back seat, the canopy has a bulge to the rear giving them a bit of a squared off look, whereas stock Mustang canopies were a pure teardrop shape.

I was going to suggest that a Google Image Search would solve the problem, but when I tried it it identified this P-51 as a P-47!

This is a P-51D Mustang. The main clue for the "D" model is the bubble canopy.
To identify it as a P-51:
It has D-day paint stripes, which means it is not an obscure prototype of some other American fighter design.
It has a belly-mounted cooling air scoop, square rudder, wingtip and elevator tip profiles, and an induction air inlet under the prop spinner- which all distinguish it from the P-40, along with the bubble canopy.
It has a 4-blade prop, which distinguishes it from the P-39.
It has the engine in the nose and no cannon firing through the prop spinner, which distinguish it from the P-39 and the P-63.

… not only probably, but certainly!

It would be great to improve this answer with the detail which identifies it as a D model (And a P-51 in general)

@Jamiec, will edit. -NN


text:
Would a flying-wing drone fly farther if filled with helium?
I'm wanting to build a flying wing designed drone and I'm wondering if I were to fill the fuselage with helium if it would improve it's range.

Not really a dupe... using H2 as fuel (most of the discussion on the "dupe" question) is full of problems. Using helium to make your wing lighter than it would be if filled with the typical atmospheric mix of N2, O2, CO2, etc, as a separate set of considerations.

@RalphJ But the main point still stands: The weight saving is miniscule. So it is a dupe.

However, the op is discussing the case of filling the (entire?) fuselage of a drone with helium, not the fuel tanks of a full size airplane.

Thank you all very much for you're incredible feedback. @CGCampbell Yes, I'm wanting to create a flying wing drone for cargo delivery with the entire fuselage being filled with helium. I'm aware that nitrogen is lighter but I don't want it to become a mini Hindenburg if something should go wrong lol.

So my idea was to create a flying wing design that incorporated a tiny compartment in the belly similar to the design seen in this vid: https://www.youtube.com/watch?v=fjjbeltn4Fo. The initial prototype of the drone would be of similar size to the one seen in the vid and would only carry a maximum of 45lbs. Since it's only a tiny compartment that would open and close for the cargo I though if I could fill the rest of the empty space in the body with helium perhaps I could extend it's range. If I should ever need to service it perhaps I could attach a valve to such the helium out and store it.

So to be clear, the actual cargo bay would NOT contain helium but the rest of the empty space in the body of the drone would. If it's of any relevance I'm conducting further research to see if a battery/supercapacitor powered drone is feasible for approx. 50 mile range with a cargo weight of 40lbs. If not then I will look into some type of combustion. After initial testing the I had intended to scale it up to something that could carry a car or two. Perhaps I would consider filling the entire drone including the cargo bay with helium or maybe just everything else except the cargo bay.

I'm not too concerned about the overall cost since I intend to create as many of the components/materials myself as possible including helium. I mean... the overall cost of the prototype can't be that of a Ferrari but I figured that if the performance increase was decent I could probably find a way to make it work at a reasonable price.

Now I wonder why nobody has pointed out so far that a flying wing has no fuselage. There is nothing to be filled with hydrogen!

Well, that's easy:  put one on there! (with a low drag coefficient).

You never specified that the aircraft was powered.  If it is a glider and you are launching it from a mountain top into the face of strong headwind, you'd improve the range by filling it with lead.

If the end result of the sealed wing filled with helium is lighter than the same wing filled with a normal atmosphere (nitrogen, oxygen, and assorted other gases), then yes - a lighter aircraft will, all else being equal, have better performance and thus longer range than a heavier one.
If you'd actually be able to achieve economic benefit is doubtful - the delta in weight will be offset by everything required to seal the wing up, and the gain in efficiency may be pretty tiny. Beyond that, if mechanics need to access stuff inside the wing, you'll be paying to replenish the helium whenever that happens. Plus, the volume inside the flying wing is normally where things like fuel, passengers, crew, cargo, engines, and etc would go; you may find that you don't have all that much available space left to fill with helium.

Helium leaks very easily, so you'd be paying to replenish the helium on a regular basis.

The weight of the sealant needed will very quickly exceed any gains from displacing air with helium, especially at altitude when thinner air is replaced by sea level pressure helium. The end result will be a weight increase and a performance decrease.

This question is interesting as it delves into the efficiency cross over point between airships and aeroplanes.
From history we learn that airships had efficiency advantages up to around 80 knots, but were bulky and hard to control in poor weather.
A drone sounds like something that may fly at slower speeds, so why not cut loose a bit and think about a lifting body hybrid.
Slower flying speeds lend themselves to very thick heavily cambered wings, or lifting surfaces which could be inflatable.
In the end it is thrust/drag expense for lift + thrust drag expense for forward velocity.  An airship drone may give you greater range.

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text:
What are differences between vortex, swirl, eddies and wake?
These terms seem to have the same meanings. Can anyone differentiate them?

I don't know what a swirl is, but here are the other terms.
Wake
Wake is the fluid flow behind a solid body or surface. It may contain vortices, eddies, or none of them (such as behind a non-lifting body or surface in an inviscid flow).
Vortex
Formally speaking, a vortex is a region of fluid flow that induces other fluid elements to circulate around it; the mathematical term for this "ability" is called vorticity. Worth pointing out is that the vortex may be really thin and confined in size. For example, in the inviscid theory, we often model the horseshoe vortex, which is actually infinitesimally thin; however, this thin vortex line will actually induce a rather large radius of fluid to circulate around it, even though they, by themselves, are irrotational.
In the wake of of a lifting surface, you'd inevitably find vortices. Even if a body or surface is non-lifting, vortices will also be present in the wake due to the shearing effect of friction, which causes fluid elements to rotate and generate vorticity, unless we are in an ideal inviscid flow.
Eddy
An eddy is a recirculating flow that is turbulent, i.e. time-varying. To sustain the recirculation, there is inevitably vorticity within the eddy. You'd find eddies in the wake of a stalled lifting surface, or in the wake of a bluff body.

Which one creates drag? The wake and eddies creates drag but vortices contribute both in lift and drag. Right?

The eddies and vortices are part of the wake, so, not right.  Better: a body of a certain shape moving through a fluid causes measurable effects, such as lift and drag (the net vector applied to the body) and disturbances in the fluid (for which we have various terms).  It's misleading to say that one effect (a kind of disturbance) causes another effect (the vector components of the applied force).

Wake is the general term for air disturbed by a passing aircraft, as might be guessed from the word's nautical origins.
Vortex (in aviation, usually a wingtip vortex) is a part of the wake that originates at the tip of a surface that has a pressure differential.  It's the preferred term in scholarly writing.
Eddy by now seems to be restricted to the name of a general model for turbulence, https://en.wikipedia.org/wiki/Large_eddy_simulation.
Swirl has a technical meaning that I can't quite fathom, but it seems to apply more to combustion in turbines than to airflow outside the aircraft.

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text:
Is hybrid propulsion widely used by UAVs?
Is it common to have hybrid propulsion in UAVs used for terrain mapping with long endurance, short range and altitude? Is the technology and research mature enough to make hybrid propulsion?
Background: I have college project of UAV design and manufacturing and I want to be a part of it as a propulsion head.

What do you mean by "hybrid propulsion"?

@jamesqf using gasoline and battery.

It's becoming common, particularly for endurance.  Two such commercially produced aircraft, Skyfront's Perimeter 8 and Avartek's Boxer, have several hours of hover endurance and a 5 kg payload capacity.
Academia is also taking note: here's a 2018 master's thesis that analyzes the advantages and challenges of hybrid power.
The core motivation for hybrid power is that the internal combustion engine can be optimized for nominal power, while the battery need only handle the difference between nominal and peak power.  That weighs less and costs less than a big IC engine or a big battery, while still enjoying the greater energy density of IC fuel as compared to batteries.
Compared to purely electric propulsion, two challenges are the engine vibration that corrupts sensor readings, and the louder noise that constrains where the aircraft may be flown without annoying others.


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Is there a specific aviation term for suicide by pilot?
CFIT, controlled flight into terrain, refers to an aircraft being unintentionally flown into the ground.
Is there any term specific for suicide by pilot?  CFIT would not apply to that situation.

According to the German Wiki article about CFIT a pilot's suicide is indeed not a CFIT. It is instead denoted as SEC.
They refer to the document CAST/ICAO Common Taxonomy Team: Aviation Occurence CategoriesPDF (Rev. 4.7, page 21)
which says

SECURITY RELATED (SEC)
Criminal/Security acts which result in accidents or incidents (per Annex 13 to the Convention on International Civil Aviation).
Usage Notes:

While security-related acts can lead to accidents as defined as by Annex 13 to the Convention on International Civil Aviation, they are not considered accidents by some organizations. Regardless, these events have similar consequences in that they result in serious injury or death to person(s) and/or substantial damage to the aircraft. For these reasons, they are categorized as security-related occurrences for prevention purposes only.

Examples include, (a) hijacking and/or aircraft theft, (b) interference with a crewmember (e.g., unruly passengers), (c) flight control interference, (d) ramp/runway/taxiway security, (e) sabotage, (f) suicide, and (g) acts of war.

Also, (same document, page 9) about CFIT:

Usage Notes:
[…]

Do not use this category for occurrences involving intentional flight into/toward terrain in manned aircraft or intentional ground impact of unmanned aircraft. […] Code all suicides under Security Related (SEC) events.

[…]

(Emphasis mine)
So according to ICAO, all suicides are SEC but not all SEC are suicides.

Well, it's one thing to say "a pilot suicide should be given the code 'SEC' rather than the code 'CFIT,'" and it's another thing entirely to say "a pilot suicide is not a CFIT." Does the German Wikipedia article really say that a pilot suicide is not a CFIT?

Yes. German Wiki says (translated) "... Also not covered by the term CFIT are accidents that occur in the following situations: ... suicide (SEC) ..." and refers to the PDF I linked to.

It's hard to prove a negative, but as far as I can tell, there is only one common term for suicide by pilot: "suicide by pilot."
The term "suicide by pilot" is clear enough and concise enough that there doesn't seem to be any reason for an alternative term to exist. The Wikipedia article Suicide by pilot only seems to mention two other terms, "pilot suicide" (essentially the same term) and "kamikaze" (which only refers to a particular set of suicide attacks).
I also searched the NTSB aircraft accident report database for "suicide" and looked through the first five results. None of them used any particular term to refer to the event besides "suicide by pilot." One described an incident as "intentional flight of the airplane into terrain in an act of suicide"; another described its incident as "intentional flight into a silo."


text:
May a US citizen fly a US ultralight into Canada?
May a US citizen (no pilot license) fly a US ultralight into Canada or any other country?
Due to a special exemption, Canadian pilots may fly a basic ultralight (registered but no certificate of airworthiness) into the US.
I don't think a US ultralight may be flown into Canada or any other country as it is not registered and does not have a certificate of airworthiness.  Is this true?

Unless you add the phrase "legally" or "in compliance with regulations", the answer has to be "yes"!

Interesting question!
Ultralights can be registered with the EAA's vehicle registration program, which issues a registration ID beginning with the letter "E". The problem is that in Canada you need a license to operate the aircraft. That is why there is no reciprocation between the US and Canada for that special exemption rule. In Canada, ultralight pilots are required to have a license. If you have a US pilot's license from Recreational on up, and an "E" registered ultralight, you are compliant with Canada's requirements. From Transport Canada's website:

Foreign licence validation certificate (for recreational pilots)
Visitors to Canada may have a foreign pilot licence validated for
private recreational purposes. The foreign pilot licence must be
valid:

under the law of the issuing state
and for privileges appropriate to the reason you’re flying

You may apply for a foreign licence validation certificate before
arriving in Canada. The certificate will be issued for a period of one
year. After a year you may renew it or apply for a permanent Canadian
pilot licence.
To learn more about the certificate, including how to apply, read
Advisory Circular 400-003: Foreign Licence Validation
Certificate.

To my knowledge, no other country has the same type of ultralight aircraft rules as the US.

@StephenS Canadian ultralight licenses are actually permits and not ICAO compliant either. But that's not relevant to Canada and the US; if they accept each other's permits then there's no issue. ICAO does not enforce license requirements, individual countries do.

That is incorrect. It varies from country to country. I have updated my answer with more relevant info about this. You can use a Rec Pilot license in Canada if it is validated.

Sec 4.0(2) does not support your claim that a license lower than Private can be validated.

@StephenS Neither does it say that it can't be. It says "private recreational purposes."

That doc lists 7 specific license types that can be validated, and the lowest is Private.


text:
If "all flying rudders" for LSA aircraft need up to 40% less area, what about "all flying elevators (stabilators)"?
If "all flying rudders" for LSA aircraft need 33%-40% less area than a typical vertical tail (stabilizer and rudder) ( subject to final stability analysis), what about "all flying elevators" (stabilators) with:

anti-servo trim tab?
no anti-servo trim tab?

I understand anti-servo tabs add stability to "all flying rudders/elevators" by auto-centering.
According to a design guide from Zenith: Flying on Your Own Wings, by Chris Heintz, pg 229:

The vertical tail area should be 12 to 15% of the wing area (15% if the rear fuselage has a small rounded section, and 12% if the rear fuselage has large flat sides). These percentages may be reduced to 7% and 10% for an "all flying rudder".

A wing is a wing, no matter what attitude, whether it be horizontal or vertical. So I should be able to reduce my horizontal tail area by roughly 33-40% when using only a "all flying elevator" (stabilator) (subject to final stability analysis).  Is this correct?
My personal view is that a Zenith can fly a lot slower with an all flying rudder, 39 mph or slower, and that is why Heintz recommends that based on the type of aircraft he manufactures: basically LSA types, @ 1320 lbs MTOW, 39-4 5mph stall speed. Somewhere I read that a Zenith 701 won a STOL competition in Australia with a 25' takeoff, and  that a 3 second takeoff is common and by the time you reach full throttle, you're aloft albeit still in ground effect.
I understand the Zenith CH200 had a classic vertical tail, but that most or all current designs use an all flying rudder.
Summary:
So I assume that Heinz's above recommendation is for sizing a rudder at a 39mph stall speed which would need to be bigger for slow speed handling than for a plane that stalls at 60mph.
Revised question: at 39 mph would an "all flying" elevator be more efficient, thus letting it be 33% to 40% smaller?

Zenith gets away with the little All Flying Rudder without an anti-servo tab because the fuselage itself is used to provide sufficient fixed fin area for acceptable passive weathervaning. If you look at their designs they all have slab sided fuselages that are quite deep all the way back.  So there is a kind of "fin" with the rudder; it's just built into the fuselage.  I got to fly the Zenith 750 demonstrator once in Mexico Missouri and I recall that its yaw stability was perfectly acceptable even though the rudder just wanted to trail if if left it to do its own thing.
Horizontal tails have more work to do and horizontal surface area of the fuselage aft won't cut it without a fixed stabilizer surface; unless you use a stabilator/anti-servo tab. If you wanted to use an all-flying surface without an anti-servo tab, you have to have a means to "fix" the surface to provide stick free static stability.  If you're in an F-86, the all flying tail is hydraulically powered and can be fixed easily with a bungee that controls where the hydraulics wants to center the surface when you're not applying force.  Some gliders use all flying tails with no tabs of any kind, and they depend on bungee springs in the pitch control circuit to provide a tendency of the surface to want to hold a certain angle if you aren't hanging on to it.
You could design your ultralight with an all flying tail with no anti-servo tab by using a fairly stiff spring bungee as your "stick free" stabilization device, and for trim. You may find the anti-servo tab method provides better handling characteristics however and if it was me I would go that way.
Note that airplanes sometimes use bungee springs in the rudder control circuit to provide a passive centering force that has the effect of increasing the fin area to improve passive weathervaning. Cessna 180/185s do this to improve yaw stability so that when fitted with floats they don't need extra ventral fins.  Problem is, it makes the rudder unpleasantly heavy.

Yes, but Chris Heintz is saying, in the quote above, that even round fuselages can reduce rudder area by 33% (15-10/15) if using an all flying rudder. A flat slided fuselage even more at about 40%.

The downside of slap sided fuselage is difficulty in cross winds.  The Curtiss C-46 with its double bubble fuselage was like a flying billboard with way too much side area and insufficient rudder area and was very limited in x winds. Anyway, the point is that it doesn't work so well in the pitch mode because the interactions are far more complex.

@ John K: re difficult in cross winds: Yes, but I think the Zenith 701 has a max x wind of 25mph, which is almost double that of a Cessna 172 at 15mph(?), so it's almost twice as good even though it has slab sided fuselage.

@ John K: Re my revised question above, would a stabilator be better at low speed handling below 39mph same as an all flying rudder, allowing it be smaller than a classical stab and elevator?

Yes you will get more tail power per unit of surface area but you have to figure out the gearing for the anti-servo tab, which will determine your stick free stability and stick forces per G.  The Cessna Cardinal's stabilator is quite large and is able to drag the tail skid on the ground as low as 30 mph (I used to own one), which is why the Cardinal has a really heavy duty tail skid.

It seems the question contains a false premise.
Why should an all-moving vertical tail need less area than the traditional arrangement, in terms of providing stability?
For the case where the pilot's feet are firm on the rudder pedals, there should be no difference, and for case where rudder is free to float, it would seem that the all-moving tail should provide less stability.
I can see why an all-moving vertical fin gives more control power to command a sideslip than a rudder of equal size attached to a fixed fin, but that's a different subject.
The above comments are for no anti-servo tab.  I'm not aware that anti-servo tabs have ever been used on all-moving vertical tails of light aircraft with simple mechanical control linkages.

The determining size of the all flying rudder may not be due to stability in this kind of aircraft with it's typical lever arm length.  Zenith could be sizing their rudder based on sideslip requirements, crosswind requirements ( 25mph vs Cessna 172 @ 15mph(?), or slow speed requirements ( 35-39mph at low weight, single pilot, I'm told).

@JohnK and Fred-- I've seen a page on a Zenith website explaining the superior crosswind capability due to the powerful effect of all-flying rudder.  Sure the slab side increases required bank angle but you aren't going to run out rudder in a wing-down correction.  The quoted material in question seems to imply though that the sizing being discussed is for stability considerations, so I still don't quite understand it.   After all it's talking about vertical fin area, and fixed vertical fin area doesn't help you deal w/ crosswinds at all, it only gives you stability.  So, I'm still puzzled.

@Fred -- see comment above.


text:
Have tried to identify the aircraft in the attached photo. It was probably taken in the late 1920's or early 1930's in California

Looks like a Kinner engine, appears to be a two person single cockpit. Resembles a Fairchild KR-21 and a Fleet type aircraft. Have not been able to locate any other similar aircraft, with these features, however gear and struts are different. Any ideas would be appreciated.

Note the distinctive geometry of the long (black) strut of the landing gear-- this will be interesting--

That gear geometry resembles a Meyers OTW, but those were dual cockpit trainers.

BTW, based on clothing, this is late 1930s or early 1940s, not a decade earlier.

Important question: where did you get this picture from?

*The Black strut appears to be a temporary brace, it looks as if there may be a 'remove before flight' tag hanging from it by the tire.

*A comment suggesting the gear may be a modification for rough fields sounds plausible, although the OTW 160 gear looks similar.

*The photo is from a collection by Burton Bundy, who operated a flying service in the 1920's in San Louis Obispo, Ca and moved to Santa Barbara in the 1930's. Not certain when or where the photo was taken, which is also what I'm trying to determine.

After gathering suggestions provided, I further researched the plane and discovered it in the 1931 Cal Poly Year Book. What I gather is the school had an aeronautics department and built 3 aircraft. One being a Warren Taperwing CP-3, which used an Arrow fuselage. The school made changes to the basic plane, as a way I suspect,  to teach students about aerodynamics and aircraft structures. Specifically the 'balloon' tires were installed in lieu of bungee on the gear, for rough fields. It was registered as an experimental acft(NX10257) This then is a one off plane. The attached photo is from the year book.The original photo I submitted, must have been just prior to the planes' completion. The person in the photo is the wife of the owner of the plane. Thank you everyone for helping me to discover the identification

George, when I added that wikipedia link to your answer, I considered noting either in the text or as a comment to you that it did include a link to Warren CP-2 as a closely related aircraft, but no photos were provided.  I had followed the link and noticed it said the plane was built on an Arrow fuselage, but didn't see the point in mentioning it since there were no photos, and since the plane in your photo seemed so similar to original Arrow in nearly all ways. Anyway you had probably already noticed that link yourself by that time.
https://en.wikipedia.org/wiki/Warren_CP-2  .

So good job on hitting it out of the park this time!  Now you really must "accept" this answer--

Yes without a photo I could not conclude this identification. However, the acft was just one piece of a puzzle I have been reservhing

I believe this is a variant of the Fleet Model 1

The Fleet Model 1 (originally the Consolidated Model 14 Husky Junior) and its derivatives were a family of two-seat trainer and sports biplanes produced in the United States and Canada in the 1920s and 1930s

Note that there were various models, with the Model 7 being the first with a Kinner powerplant.

Another view of a Model 10, with a similar aspect to your original for comparison

Things that make me think this answer is right:

The geometry and shape of the balanced rudder
The semi-circular cut-out to the rear of the upper wing
Shape and location of struts and  guy wires (although both were quite common in many models of biplane of the era!)
The engine cylinders exposed around the cowling (albeit this particular engine was used in a few, but not that many aircraft)
The general similarity between the look of the fuselage and its particular construction (especially the first picture above)

Things that cause me to second-guess myself, and that this might be the wrong answer

The odd strut going from undercarriage to upper cabane strut (Although as noted elsewhere, aircraft of this era were built with so many variants, and sometimes modified for a specific purpose such as rough fields which may have required bigger wheels and the strengthening of the undercarriage - could this be the reason for it? I was unable to find any picture with this modeification though)
The quite apparant different dihederal of the lower wing
This model of aircraft was primarily built as a two seater, and the original picture looks like it clearly has just a single cockpit.
The cowling looks too elongated in the original picture to be a Fleet Model (but again could this have been a modification?)

I think it is hard to be 100% sure this is the right aircraft as shown.

@quietflyer you may well be right - it wouldnt be the first time I was sure I had the right identification and someone much more knowledgable comes along and proves me wrong. In my favour, there were a lot of variants of this particular model.

The rudder, shape of the nose, wing cut out for the cockpit, wing struts, wing shape, fabric covered fuselage, engine and guy wires all lead to conclude this is a Fleet. The gear and single cockpit is still puzzling. The gear may be a post manufacture modification and I can check the approved changes of that era. If the forward cockpit was covered or deleted, it was done with great work, however, this may also have been one of the few manufactured with just a single cockpit.

I have received suggestions from others, one of which most closely resembles the aircraft in the photo I submitted.....Arrow Sport.
There were modifications made to the original design and variants were manufactured of the 100 total built. It is a single cockpit, two seat(side by side) design, which had two sets of controls for training purposes.
The issue with the rudder having a'horn' in my photograph and a number of Arrow Sport photos, that do not have a 'horn', is basically the only the major difference. A number of variants and changes were made through the early years and this may have been one. A couple of the modifications made included the outboard wing(N) struts and guy wires and engine types.
Here's a link to the Wikipedia page on the Arrow Sport.

The strut from the gear to the inboard N on the Arrow Sport looks very similar to the arrangement in your photo

Tapered lower wing shows well in third photo in Wikipedia link, tapered upper wing is also somewhat evident.  In upper wing it's pretty clear the taper is partly due to slightly swept leading edge, which may be at variance w/ photo in original question, or it may just be hard to see at that angle.  This photo -- https://en.wikipedia.org/wiki/Arrow_Sport#/media/File:Arrow_Sport,_Lincoln_Airport,_Lincoln,_Nebraska,_USA.jpg .

The long gear strut on all Arrow Sports has a faired rubber spring which is clearly missing in the airplane in question. I'm not convinced, but also have no idea what the plane in the picture is.

The photo referenced in my previous comment also clearly shows the trailing edge of the lower wing, at the root, well below the bottom of the fuselage, as in the photo in the question -- one feature I failed to point out in my own "answer".   The author of this answer might wish to consider incorporating some of these additional ID points into the answer.

While this community has a huge knowledge base, and these kind of questions quickly attract precise and correct answers, I am not convinced any of the answers here, as they now stand hit the nail on the head, the answer by JamieC being the closest match IMO.
Just as JamieC, I'm quite convinced this is a representative from the Fleet Model 1 "family tree", but I'm certain this is a special  one-off plane based on the following observations, "internet research" findings, and conclusions thereof. Most of these findings have already been posted in previous answers, but I'm relisting the here for consistency.
Fleet Model 1 family is by far the closest match to the overall posture and form of the plane in the picture. None of the Fleet Model 1 through 21 pictures I was able to find are a perfect match, but as Wikipedia states, variants of the Model 1 are numerous, including many one-offs. Other proposed planes differ substantially in such features as tailplane and fuselage cross section form, these are commonly quite stable design elements, and are seldom "fluid" among aircraft models.
The most notable differences for your garden variety member of Model 1 family are the lack of second seat, zero dihedral of the lower wing, extra landing gear strut and the oddly bulky tires. Smaller deviations are the deep cockpit cutout and elongated nose, latter may just be a visual misconception due to a wide angle lens.
Especially the single seat, landing gear assembly and the tire lead me to believe this is a special purpose plane, built for a pilot handling the plane rougher than usual, which lead me to this picture on aerofiles.com site:

The gentleman in the picture is one Paul Mantz, a prominent Hollywood stunt pilot, air racer and charter service provider. The thing that caught my eye was the tire Mantz is resting his foot on: clearly the same type shown in the picture at the question. Mantz used Fleet planes in his work as a stunt pilot, and it is not far fetched to assume he must have had connections with Reuben H. Fleet, the founder of Fleet Aircraft. This interaction may have spun off planes such as the one in the question.
One more thing suggesting a special purpose of this plane is the lack of dihedral in the lower wing. Biplanes are quite stable (in roll axis)  due to the center of lift being high in relation to the center of gravity. Dihedral would further increase the stability, and this may not have been preferred by a stunt pilot.
A feature that puzzles me is the droop of the inner portion of the lower wing. Up untill now I have not been able to make sense of its purpose.
As for the picture itself, it is clearly not just a snapshot taken by someone wondering past a plane with his girl. There is artificial lighting in use, coming at least from two sources, the positioning of the plane is not "natural, as there seems to be no good reason for it to point in that direction other than that it forms the best composition with its surroundings being placed such. The lighting, composition and the wing ribs hanging on the wall make it clear to me much thought was put into setting up this picture.
The picture and the lady may be related to a movie of the era, for example on featuring Mantz as a stunt pilot (for a comprehensive list of Mantz's work, see IMDB). Closest match of actresses in these films might be Isabel Jewell, but this is a long shot. The picture may also be "just" a portrait; Phyllis Fleet, daugter of Reuben Fleet was an avid aviator, but she does not quite match the picture, being too tall for the timeframe. Mr. Fleet had two daughters from his second marriage, Dorothy and Nancy, neither of which are unfortunately traceable with means at my use.
And, to drift just one step deeper down the rabbit hole, one more possibility: Nancy Love was a famous WASP; Women Airforce Service Pilot, who has a link to a Fleet "frankenplane":

Love was hooked on flight at an early age. At sixteen, after just four hours of instruction, she flew solo “a rather broken down Fleet biplane that my barnstorming instructor imported from parts unknown.”

So in addition to being a poster movie, a personal portrait of a member of an aviation family, this picture may also have ties to the WASP program.
Getting back on track, the plane itself is most likely a model produced for a very specific purpose, be it show or stunt flying, racing or just a wealthy pilot's toy. Single seat biplanes are not exactly a common sight, and never were, not at least in civilian aviation. It also possible it may just be "prop", a  non-flying showpiece put together of pieces of Fleet planes, but this seems a bit far fetched as all the technical details seem to be in order (aside from the lower wing dihedral).
Those with better (meaning non-internet, I've dug that inside and out) access to sources containing information about Mantz, the Fleet family saga and the original source of the picture, the  collection by Burton Bundy will most likely be able to expound on this line of thought.
Take heed, I may expand this rant even further.

This is not meant to be a complete answer, but may help in the quest to find one-- it appears that the upper wing has some taper, i.e. the root chord (just outboard of the cutout) is significantly wider than the chord near the wing tip. Parallel lines should converge in the distance, and if you lay a ruler on the leading edge and trailing edge of the aircraft's upper left wing, those lines diverge, not converge, if you extend them far beyond the left edge of the photo. The taper appears to be entirely due to forward sweep on the trailing edge-- the leading edge appears to be unswept.  I'm not seeing that same taper in photos associated with any answers posted up to this point.
A close look at the bottom wing suggests that similar taper may be present there too.
It also appears that both the top and bottom sets of wings have essentially zero dihedral, which also seems at variance with photos associated with answers posted up to this point.  (The bottom wing may have just a hint of dihedral, but not much, no more than one or two degrees.)
Of course, it has been noted that some of these planes were produced in many variants.
A further note-- each of the main landing gear wheels is supported by three struts.  The middle struts meet the bottom of the "cabane" struts, like on the Meyers OTW 160.  The forward struts connect to the lower sides of the fuselage-- they don't meet together at the bottom of the fuselage as is the case with some other aircraft with rather similar landing gear geometry such as the Meyers OTW 160.  Similarly, on the aircraft in the question, rather than meeting together on the bottom of the fuselage, the aft struts for the landing gear connect to the fuselage quite far apart, near the root of each the lower wings (and aft of the leading edges of the lower wings).  The small white vertical rectangle above the aircraft's left tire is the aft strut for that wheel, highly foreshortened by the viewing angle, while the aft strut for the right wheel is more clearly visible in the photo, though its actual point of attachment to the fuselage near the wing root is hidden by the standing figure.
On first glance the photo gives the impression that two landing gear struts meet together, or cross in close proximity to each other, behind the standing figure, but that's not actually the case, and those two struts are not actually a matched pair-- they are the aft strut of the aircraft's right wheel and the forward strut of the aircraft's left wheel, and they are widely separated in the fore-and-aft direction.

As for the comment on variants: worth noting also are the oddly wide tires. I'm certain this is a Fleet Model something, modified for soft/poor airstrips, hence the extra strut and the "offroad" tires.

Partial answers are indeed fine, but you've just described the picture in the OP. I dont see how that answers the question, even partially.

This does not provide an answer to the question. To critique or request clarification from an author, leave a comment below their post. - From Review

@Jamiec --  "but you've just described the picture in the OP" -- my intent was to bring attention to details that may not have been immediately obvious.

@Pondlife -- my intent was to bring attention to details that may not have been immediately obvious, that may help in constructing an answer to the question.

@quietflyer great, but that's not an answer!

@quietflyer I agree it's helpful to give pointers and suggestions to get to a better answer, and in the StackExchange world that's what comments are for. If we allow answers that don't answer the question and just make suggestions or even raise other questions then we have a discussion forum, not a Q&A site. SE is explicitly trying to avoid the discussion forum format. That's my take on it, anyway.

@Pondlife -- so in your opinion much of the content in my "answer" would be acceptable as comments to the question?  I'm not sure that view would be widely shared; I think some people would construe them as "partial answers", and not things that are intended specifically to improve the question itself, which as I understand it is the intended purpose for comments to questions.  Well, this will probably eventually find its way to "meta" --

@quietflyer Yes, I think things like this belong in comments. Others may disagree, as you said.

@Pondlife -- (of course, could also be posted as comments to answers that seem to be contradicted by this info-- but then we're slipping back into "discussion" mode aren't we?)

"near the root of each the lower wings " -- should be "near the root of each of the lower wings "

@quietflyer Why not move all this info to a chat room and leave a link to that chat under the question?

Sorry for the rubbish lock reason. But as you've been asked before please stop making minor edits constantly. If you wanted to make a significant edit which actuallly answers the question feel free to flag this and we'll unlock it straight away

Given the relatively short list of aircraft for which the Kinner R5 family was an original or retrofit powerplant, and the very distinctive landing gear strut geometry, I'm pretty sure this is a Meyers OTW 160.  The OTW were built with various engines; the 160 model had a 160 HP Kinner R5.
The only uncertainty is that the OTW line were, as far as I can determine, all built as dual cockpit trainers; it's very possible this one has had the front cockpit deleted or a very well matched cockpit cover fitted (cockpit covers, especially, were fairly common when the OTW were built, as they kept weather out of the front cockpit when the aircraft was tied down or when being flown solo).
As noted in comments, this aircraft type saw some minor variations over its production.  Besides being sold with at least three different engines, there were changes in fin/rudder shape, some had fairings on the long struts above the landing gear while others didn't, I've found at least one photo showing a matching front cockpit cover, and while as noted in comments, the OTW has some dihedral in the upper wing, it was subtle enough to be hard to see from certain angles and positions.

(source: airport-data.com)

Those a/c appear to have at least a mild amount of dihedral in the upper wing, which I don't see in this photo.  A good example where this shows is 4th photo down in this website http://www.aviation-history.com/meyers/otw.html  .  Note also very large rudder, and struts bracing horizontal stab to vertical stab --

Based on photos I found via Google, there were a number of minor variations -- not to mention four distinct models with different original engines (some of which were later re-engined with the Kinner).

The Consolidated N2N-1 has 1.  a more similar, curved upper wing cutout 2. a more similar tail brace cable 3. a more similar doubled up wing brace cable 4. faceted fuselage.  I think none of the pictures posted yet show the right landing gear.

I just noticed, that the front struts of the landing gear of the aircraft in the photo appear to meet the fuselage further apart on the sides, rather than joining together at the bottom of the fuselage as w/ these aircraft.

@AnonymousPhysicist If you have a better answer, then please post a better answer.  I started with a search on what aircraft had been built with Kinner radial engines, but it's entirely possible that almost any biplane in this size range could have been re-engined with a Kinner during the period when they were manufactured (or even after -- homebuilders fairly frequently install obsolete engines because they're inexpensive).

@quietflyer I initially thought that was the case as well, but concluded it was an optical illusion.  Careful examination of the OP's image also seems to show the front cockpit cover, though the front windscreen seems to have been removed (as would make sense if you were semi-permanently making the aircraft a single-seater).

@ZeissIkon -- re landing gear -- see my answer (edited yet again recently) -- last couple of paragraphs-- does that help?  On another note, observation of cockpit cover seems worth including in answer if you are sure it's there-- (or even if not sure )

I believe the upper part of the front strut of the plane's left wheel, including the point of connection with the fuselage, is entirely hidden behind the standing girl/ woman


text:
Does propwash increase pitch stability?
Here is a polar for a piston single-engine aircraft:

(This is lifted from a Russian manual for Yak-52, so $C_x$ is drag, $C_D$, and $C_y$ is lift, $C_L$).
1 is the 'normal' case without propwash. 2 is nominal, and 3 is the max takeoff power.
It is evident that the whole lift curve slope $C_L^{\alpha}$ is increased significantly (by some 30%) as the engine revs up, with $C_{L_{max}}$ reaching 2.
But what immediately follows, amongst other things, is that the AoA (pitch) stability should increase accordingly: it is proportional to $C_L^{\alpha}$ (as well as to the distance from NP to CG).
However, somehow I've never seen this fact mentioned explicitly, despite it being quite significant. Can anyone confirm it, either from literature of experience flying higher-powered prop aircraft?
(It may not be very obvious to feel the difference because other conditions are rarely the same between idle and full power, but the closest approximation I can think of is glide descent vs full power climb at the same speed: the aircraft should be 'stiffer' and possibly more oscillatory in pitch at full power. However, propwash over tail may mask this effect; perhaps a twin is a better testbed for this...)

At first glance, this seems to not take into account P-factor and the need to apply rudder to compensate?

@Juan, this is a totally different effect. Here I'm trying to isolate specifically the lift/pitch effect of propwash over wings.

@Zeus "stiffer" is consistent with higher speed effects, the plane becomes so stable and deflection of elevator so difficult the plane cannot pull out (of the dive). Oscillatory would indicate directionally unstable, but it would be interesting to see (if ever) the entire plane developed a feedback "flutter".  If there was some bending in the fuse, maybe, but at that point it would probably be coming apart.

If the plane becomes somehow more stable at the same speed (e.g., in the trivial case, by moving CG forward), it will feel 'stiffer': that is, greater effort will be needed to manoeuvre it. Maybe that's not the best word because it may imply less movement, but that's how people describe it: movement is much less relevant than the force for us. Oscillations may arise if the system is overly stable but damping is not sufficient; this again may happen if you increase stability without changing the aerodynamic configuration, like when moving CG. It can happen in pitch just as well as in yaw.

And in roll too!  An oscillation in pitch probably would require large amounts of pitch torque from mass away from CG.  Fortunately, in aircraft design, this is rare (although you can create a phugoid with poor matching of CG and elevator trim).  "Stiffness" definitely was an issue when aircraft with manually controlled surfaces progessed past 300, then 400 mph.  An interesting match when combined with the unstabilizing effect of the puller prop Peter K pointed out.

I'll have to double check that for large, heavy aircraft with small tails!  (and no propwash).

There is not an obvious answer to this. I'll outline three effects (among others):

Placement of thrust line. If the thrust line is placed below the CG, it will have a destabilizing effect; the converse is true. That's why wing mounted engines tend to destabilize aircraft as throttles are increased. But that's not the title of your question.
The local increase in flow from prop wash increases the wing lift slope. This tends to decrease the pitch stability. An increase in lift has an associated increase in downwash as a function of AOA. This also tends to decrease stability.
The local increase in flow from prop wash increases the tail lift slope. This tends to increase the pitch stability.

The neutral point contribution is as follows (cited from Etkins, Dynamics of Flight):
$$h_n=h_{n_{wb}}+\frac{a_t}{a}\overline{V_H}(1-\frac{\partial\epsilon}{\partial\alpha})-\frac{1}{a}\frac{\partial C_{m_p}}{\partial\alpha}$$
where $h_n$ is the location of neutral point, $h_{n_{wb}}$ is the wingbody aerodynamic center (AC), $\overline{V_H}$ is the tail volume with respect to the wingbody AC, $a_t$ is tail lift slope, $a$ is the total aircraft lift slope, $\epsilon$ is downwash on the tail, $C_{m_p}$ is the pitch moment contribution from thrust.
Forget about thrust line for a moment, then we have:
$$h_n=h_{n_{wb}}+\frac{a_t}{a}\overline{V_H}(1-\frac{\partial\epsilon}{\partial\alpha})$$
Therefore, increasing the wing lift slope decreases the neutral point, as will an increase in downwash. Increasing the tail lift slope has the opposite effect.
So there is no blanket statement.

I'm trying to concentrate purely on the effect of the polar change, i.e. on (2), and specifically on the AoA stability. (1) is clear and is a very different effect. For (3) it would be interesting to learn in what proportion the tail lift slope changes vs the wing's, but for the moment let's remove the tail from the propwash (on a high T, for example). So, for (2), why does it decrease the pitch stability? As I noted in commens to the @Peter's answer, in my mind it shouldn't necessarily... On the other hand, the effect of the increased downwash must be significant, thanks for pointing out.

@Zeus I've added some math in my answer to show the rationale

One way of looking at it are helicopter rotors, where forward motion will increase the Clift graph the same way. Another thought is to consider the prop blast perhaps as a local source of air velocity, maybe having more effect on the front of the wing?  But management of thrust line, and impingement effects on the entire aircraft, may be were we want to go with these new, incredibly powerful fans.  Older designs successfully mounted props smack in front of the wings, or on the nose, for a long time.

@Jimmy, thanks. It's much clearer now. (I would dare to suggest to explain $V_H$ as well just for completeness; I know it's the 'tail volume', and btw the way Etkin uses it it should have overscore meaning it's related to AC rather than CG). It would be interesting to know though in what proportion the tail slope $a_t$ changes vs $a$ in practice when the tail is in the same wash... But that's another question.

Good catch. I've modified the answer to show meaning of VH.

No. Only for pusher types it does.
Pitch stability is the change in pitching moment over angle of attack. The polar doesn't mention this and I would expect that pitch stability decreases with power.
Pitch stability is $$\frac{X_N - X_S}{l_{\mu}} = -\frac{c_{M\alpha}}{c_{L\alpha}}$$ and with an increase in $c_{L\alpha}$ the absolute value of the whole term should become smaller. That would be normal for tractor propeller aircraft, see this answer. Note especially the reference to an old NACA report (NACA TN 2586) on this by John L. Crigler and Jean Gilman, called Propellers in Pitch and Yaw.
In order to measure pitch stability in flight just measure the stick travel needed to trim different airspeeds for the fixed-stick stability or the stick force needed to trim different airspeeds (without changing the trim setting, of course!) for the stability with free-floating elevator. Both should decrease with power on.

This would be absolutely correct when comparing a glide and powered flight at the same speed for tractor (puller) prop.  Is it possible that increased airflow over the wing trailing edges and tail somewhat counteracts the prop effect?  (Getting glide and powered handling close would be a plus for design).

@Peter, that's what I generally knew but such a large change confused me. I made a childish mistake of mixing the wing AC and overall AC (NP). Still, if it's fair to say that the whole effect is caused by the local increase of airspeed on a part of the wing (assuming perfect axial propwash), the AC won't move, and both $c_{M\alpha}$ and $c_{L\alpha}$ of the wing will change proportionally, causing no change in stability - if we remove the tail from propwash for a moment. There will be destabilising effect due to increase of downwash-per-alpha, which we can't exclude, but is it the main cause?

...Interestingly, $c_{M0}$ must change: the absolute moment on the affected part of the wing will increase, so if we still want to relate the overall moment to the whole wing, we need to change the coefficient as a function of propwash/power. But this is not a consideration for pitch stability: it doesn't depend on $\alpha$. It may shift the trim with power, but in reality the propwash effects on the tail will probably override this change.

As for stability increase for pusher props, the cause still eludes me. The NACA report essentially talks about the cross moment: yawing for a pitched prop etc. - the cause of the famous 'P-factor'. But it doesn't show any significant pitch moment. If so, the effect must be caused purely by the aerodynamic effects of the propwash (or suction before the prop?) That's worth a separate question though...

@Zeus: Propwash is only part of the answer. The thrust vector of a propeller shifts with angle of attack and sideslip changes and also is only parallel to the propeller's axis of rotation for zero angle of attack and sideslip. The NACA report contains more than only the p-factor: A propeller acts similar to another tail (or canard) surface; it contributes its own c$_{L\alpha}$ so a tractor propeller's change in thrust with angle of attack destabilizes the aircraft all by itself.

Agh! Another childish mistake: I forgot that lift (and all other aerodynamic forces) are expressed in the wind axes! Of course, in the wind axes just the normal thrust component itself will have enormous effect. For props, there must also be some additional damping, but it should work for both the pusher and tractor the same way. Nevertheless, this effect doesn't seem to be the point of that particular report. Now, with this (major) effect clear, I'm still curious about the polar change effect alone, if only for academic reasons...

Thanks for including the identity of the aircraft.  The Yak 52 is a low wing single engined tractor design.  The graph indicates prop blast over WING increases its lift at a given angle of attack.
It does not seem possible to infer anything else from that graph and I would not wish to guess.  The prop blast could affect the horizontal stabilizer trim and improve the directional stability, which includes pitch (and yaw). This would be a reasonable generic assumption for all aircraft of this design, with the caveat that prop flow swirl could also have effects on the empennage as well.
However, I doubt the Yak designers would leave it with borderline stability without prop blast.
The test would be to glide it.  Under power, trim may have to be adjusted, as is normal for aircraft of this type.


text:
What is this strange looking aircraft?
This website describes twin-tail aircraft. It has a photo of a strange-looking aircraft with a twin tail, and turboprop engines, resembling a C-130 Hercules.

There was no registration or tail number on the aircraft. I looked around at other images trying to find the name, but it did not feature the same aircraft. The aircraft looks fictitious.

The tail resembles an-225 so the logical thing is to check antonov wikipedia.

The An-22 is much larger than a Hercules.

@Peter, nevertheless Hercules managed to beat Antaeus ;)

"aircraft looks fictitious" almost always means former Soviet.

That is an Antonov An-22 “Antei”.

It really kinda looks like the photo has had markings effaced for some reason that suited the posting site. Very unlikely an aircraft in a non-stealth paint scheme wouldn't have registrations, flags, any kind of marking. I do find that a reverse photo search includes https://www.icepop.com/largest-military-planes, on which there is a photo which but for the terrain features could be a flipped copy of this, with the markings present and the aircraft identified.

That's two related photos over the same terrain, with a few seconds between them and one flipped.

@CCTO: Yes nearly the same image (comparison). Same shadows, and amazingly, nearly the same blade angular positions.


text:
Who was the first person to break the sound barrier?
In this video on Wikipedia of Chuck Yeager breaking the sound barrier in the Bell X-1 in level flight, at 2:44 the narrator says "For the first time, except in dive, a man has flown an airplane faster than the speed of sound."
Was the sound barrier recorded being broken previously to the X-1 by someone else in a dive? I can't find any information online about this.

Check the section "Early Claims" on page: https://en.wikipedia.org/wiki/Sound_barrier
There are multiple claims of people breaking the barrier in a dive. But many are disputed.

For instance, there was a claim that an Me-163 Komet became (at least) transonic after being towed to altitude with full tanks and air started (hence not spending most of its fuel climbing) -- but post-War testing suggested the airframe would become uncontrollable above about Mach 0.9, IIRC.

@Zeiss Ikon: Is there any requirement that the person/aircraft breaking the sound barrier actually has to survive the experience?

Ask the questioner -- but if not, there were surely some folks back in Ottoman days who did it after being shot from a cannon...

@Zeiss Ikon: I was actually thinking more of WWII fighters like that  Komet.  In dogfights the pilot starts a dive with power, then is shot, passes out, or is otherwise disabled, and the aircraft continues straight down under power.

@jamesqf Generally, propeller fighter designs would become unstable due to shock wave formation and break up from excessive G load before they get "supersonic" -- they'd be overall around Mach 0.8 or so when that happens.  This was the reported cause of several crashes of the faster, "cleaner" propeller fighters (P-38, for instance) late in the War and immediately after.

@abelenky That early claim section is really interesting. I suppose I was most interested in who the narrator of the X-1 video could be referencing. I guess he might not have had anyone in mind?

There was actually a pilot in the testing of the F-86 Sabre who may have broken the sound barrier in a shallow dive without telling ground control before the X-1 broke it. There is no definitive proof of it, but there were odd trails reported in the sky...

Many an aviator prior to that broke the sound barrier… for a few, terrifying moments.

A pity that the film's author, producer, narrator are unnamed.  We might have been able to ask them why they said that.

Short answer

Was the sound barrier recorded being broken previously to the X-1 by someone else in a dive?

The factual answer is: Such recording wasn't found as of 2024. Considering the great sensation Yeager's flight had in engineering community, if a record existed for flying supersonic before him, even in a dive, there is no doubt it would have surfaced.

Who was the first person to break the sound barrier?

This question cannot be answered except by: It's possible someone did fly supersonic before Yeager 1947 flight. Most claims are not credible, but two are, both cases in a powered dive:

Hans Guido Mutke in a Messerschmitt Me-262, in 1945.
George Welch in a XP-86 prototype, in 1947, 20 minutes before Yeager (repeating a flight without witnesses 13 days ago).

There is a well-detailed article: Was Chuck Yeager the First to Break the Sound Barrier? at skeptoid.com providing factual elements and good analyses. I'm copying parts of these analyses for the different types of claims. You should read the complete original article to get the full story.
Hans Guido Mutke and the Messerschmitt Me-262: Credible
Hans Guido Mutke flying the Messerschmitt Me-262, the first jet engine aircraft that could have defeated the Allies.

Mutke was cruising at 36,000 feet when he began a steep dive under full power. With his airspeed indicator pegged at its limit of 1,100 kph [...], Mutke reported severe buffeting and loss of control. Suddenly the buffeting stopped and he regained control, with the airspeed indicator still pegged; and it's this that could indicate he had broken the sound barrier.

The manufacturer considered this aicraft couldn't fly supersonic:

Willy Messerschmitt, always stated emphatically that the 262 was incapable of supersonic flight. In flight tests, he found that at Mach 0.86, the 262 experienced Mach tuck: It lost control and assumed a nose-down attitude that could not be corrected by the pilot, and throttling down was the only way to resume control.

However Messerschmitt didn't take into account one detail:

The tailplane was actually all-moving for trim purposes. This was a separate electrically operated control, and it was normally used to keep the plane level as its fuel supply was consumed.

A large all-moving surface was actually a solution to escape Mach tuck and keep control surfaces effective, contrary to a fixed stabilizer with elevators.

Mutke reported that he actually employed this all-moving trim control in order to get out of the nose-down state, a technique which may not have been considered in Messerschmitt's own tests. Mutke's report was given additional credibility in 1999, when computer modeling and scale model wind tunnel testing conducted at Munich Technical University found that the 262 was capable of reaching, and passing, Mach 1.

This is a credible case of supersonic flight. However no record was kept.
George Welch in a XP-86 prototype: Highly credible
The most credible dive case which may be the one suggested by the narrator in your video. This test pilot claimed flying supersonic 13 days before Yeager's flight with a fighter prototype, the XP-86 in a powered dive. But this wasn't provable, so he decided to repeat the experience just minutes before Yeager's flight, when Yeager's X-1 was still attached to the B-29.

Welch again put his XP-86 into a steep dive. Some stories say that he buzzed the B-29 close enough for those onboard, Yeager included, to hear his sonic boom. He made a 4g pullout from his dive, and those same stories say that his sonic boom was louder than Yeager's just 20 minutes later.

This was technically possible as:

The history books credit George Welch with breaking the sound barrier in the XP-86 in a dive six months later on April 26, 1948, with official measurements and a proper Mach indicator on board.

Now the cases that don't count as supersonic flights.

Unintentional: Certain, but aircraft destructed
Unintentional supersonic flights during WWII are certain, but such flights don't count as controlled flights, the aircraft was destructed while accelerating to supersonic velocity. The reasons are the oscillating shockwave triggering buffeting and preventing control surfaces to work, and the Mach tuck phenomenon starting below Mach 1 on wings not designed to be sonic.

Dive bombers had to have special air brakes developed to prevent them from breaking up, which sometimes happened anyway. Of the many pilots who toyed with the sound barrier in WWII — all unintentionally, of course — most never survived the adventure.

Planes that had been shot down often entered the transonic realm as they plummeted, and were torn apart by the resulting shockwaves.

Claims with propeller aircraft: Impossible
Apart from diving, there were claims of being supersonic with propeller aircraft. This is impossible as the propeller is supersonic before the aircraft is supersonic. Supersonic blades are stalled, thrust disappears, the aircraft slows down.

Supermarine Spitfire, the Lockheed P-38 Lightning, and the North American P-51 Mustang, experienced these effects at Mach 0.85.

Heini Dittmar and the Messerschmitt 163 Komet: Improbable
There are claims of this aircraft flying supersonic. Being rocket-powered this aircraft was not limited by stalled propellers. Its delta wing would allow transonic speeds, but not the control surfaces.

In combination with the relatively low 3,800-lb thrust of the Komet's Walter rocket engine (about half the power of Yeager's X-1), the Komet had little expectation of going supersonic, except in an uncontrollable, powered dive which would probably be unrecoverable.

Heini Dittmar was a Komet test pilot. Test pilot and friend Mano Ziegler published a book in 1990, claiming Dittmar broke the sound barrier:

One unofficial report claims that Dittmar hit 1,130 kph in 1944 (Mach 1.06), and another states that in a steep dive he created sonic booms that were heard on the ground.

But there is no trace of these events in the manufacturer archives:

The best evidence against Komets breaking the sound barrier is the fact that the Allies did capture all of the program's classified data, and no supersonic flights were ever recorded, even in secret.

And this is technically improbable:

With its delta wing, the Komet had no tailplane at all, let alone an all-moving tailplane. It had fabric-covered elevons on the trailing edge of the delta wing, which would always be shock stalled.

Even if a pilot opened his Komet's rocket engine to full throttle to muscle his way past the sound barrier, Mach tuck would send him tumbling out of control irrecoverably, and probably destroy the airframe.

Claims solely based on airspeed indicator: This is not a proof
Aircraft had pitot-based airspeed indicator not accurate to measure sonic speeds.

A phenomenon called compressibility error gives inaccurately high airspeed readings as the aircraft approaches the speed of sound. This error is called Mach jump. To counter this, supersonic aircraft use a Mach indicator instead of an airspeed indicator.

What Dittmar did was to exceed 1000 km/h first, in a 163A. BTW, in that flight he lost almost all of his rudder. Maybe people later confused that with breaking the sound barrier, but with a tailless airplane that is extremely unlikely. Compare with the unfortunate ends of all three DH.108.

Concerning high speed dives: The Me-109 also had a trimmable tailplane and in 1943 test pilot Lukas Schmidt was to find out why some pilots would dive to their death from high altitude. He reached up to Mach 0.805 but could only pull out using the trimmable tailplane at low altitude because the trim jackscrew was lubricated with fat containing water, which would freeze the jackscrew solid at high altitude. Using the elevator alone required superhuman strength to pull out, only a trim change could end the dive. Consequently, Messerschmitt switched to water-free lubricants in 1943.

There is a possibility that German pilot, Hans Guido Mutke, had broken the sound barrier in a Messerschmitt Me 262 on April 9th, 1945 after diving approximately 3 miles.
As others have mentioned, there is no documentation or way to record this as accurate with instrumentation since the airplane's airspeed indicator was maxed out at 1100kph/683mph/594kts, it was not calibrated with the intention of setting any records, and there were no other witnesses than the pilot.
I suppose someone could possibly test this out "Mythbuster's style" in the future once we get the automated airplane tech figured out or maybe use simulation technology to see if it would have been possible in this type of aircraft without it experiencing a catastrophic failure.

It is unlikely WWII era aircraft had instruments that measured mach. So any claims to having gone supersonic could not be proven. If you knew how it felt to pass through the mach, you might claim it, but again no way to prove it.
My fastest: mach 1.82.

Many issues here. Whether WWII era aircraft likely or unlikely to have had instruments that measured Mach doesn't substantiate anything. The answer to the question of the OP does not hinge on availability of instruments in aircraft. So your claim that any claims to having gone supersonic could not be proven is also wrong, because having gone supersonic would not necessarily depend on instruments that were built in the aircraft. In addition, "could not be proven" goes to far, because even if claims were not proven does not mean they could not be proven. Many things in life could be proven

I don't think early mechanical machmeters were really any better than a standard airspeed indicator and altimeter, they just did the math for you.  As long as a pilot noted their airspeed and altitude they (or someone else) could later calculate their Mach number.  Lacking temperature info it wouldn't have been totally accurate, but neither were the original machmeters which didn't have temperature input. What would matter though is whether the airspeed indicator went high enough.

Many WWII fighter could approach Mach 1 in a dive. I believe after the war a P51 reached 0.85 Mach in a steep dive.
There were several undocumented claims that based on indicated airspeed a few planes had managed to reach Mach 1 in a dive.
It is well known that many planes broke up as they approached the transonic region starting around 0.8 Mach.
Most Engineers doubt that any WWII aircraft could have survived breaking the sound barrier.

The problem was less breaking up but becoming uncontrollable from Mach tuck. There were dozens of cases of dives of fighters during WW II that went straight into the ground.


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Novel Research: Best way to sabotage a Hawker Hurricane in 1940/41?
Essentially, one of the central events in my work-in-progress novel is the sabotage of a Hawker Hurricane in Malta by a member of groundcrew. I originally had this as him loosening an aileron so that it falls away during the climb, with the pilot then experiencing loss of roll control and coming down to crash-land. I've been advised, though, that this would be picked up in pre-flight checks and that it might be more feasible if the control cables inside the wing or rear fuselage were damaged/cut. Do either of those scenarios sound plausible? And what kind of height would the pilot be able to climb to before realising something is wrong and having to come back down? The idea is that the pilot has to force-land and that he is badly burnt/injured but ultimately survives.
Any thoughts/guidance greatly appreciated. Aware it's a slightly niche/leftfield question to be asking but thankful for any response.

Pilots almost always verify that the flight controls respond correctly prior to takeoff, in which case, issues with the cables would become quickly evident. Even if the pilot couldn't see that the surface wasn't moving, he'd feel that the tension/pressure/resistance on the stick was lower than usual in one direction.

I think a bit of clarification would be helpful.  Are you looking to just cause the plane to not be able to fulfill its mission, but be able to return safely to base, or do you want a catastrophic failure that would cause a crash and likely pilot injury or death?  Also, do you want it detectable, or "act of god" type of failure that can't be identified, even if the pilot/aircraft makes it back safely?

The Achilles heel, a good single-point-of-failure source that will be hard to detect until it's too late, of a plane like a Hurricane would be coolant system.
If I was going to sabotage a Hurricane in a way that forces it to return to base while enroute, and that is unlikely to be detected until it's on its way to combat, is to loosen a coolant line fitting, running to the radiator in the belly, such that it holds together initially, but starts to leak when the heat and pressure build up during the climb to altitude.
So during the climb to intercept, the coolant temperature goes haywire as the coolant is lost, pilot is last one in the flight so no one spots the leak and it isn't discovered until it's too late, pilot is forced to descend back to base, engine overheats on the way and has to be shut down, pilot lands short of base in rough terrain and is injured in the crash landing.

Good answer. If the coolant line was near the engine, a leak could obscure the vision of the pilot. This would make even a landing back at the home base hazardous.

I would imagine the pilot would rather run the engine till It died trying to make it back to base rather than shutting it down only to wreck the whole plane... That is unless he thought he had a good chance of landing it safely and accidently messed it up.

@Zock77 Depends on terrain : Hurricanes often operated from grass strips so any convenient field would do at a pinch. But, Malta being an island, you'd at least have to make it to land (and it's rugged terrain, so not many choices when you did) so this works.

What a foolish pilot to ride a broken aircraft into terrain instead of bailing out to protect the more valuable asset, himself, as he was trained.

@Jasen, not necessarily - if you've reached parachute height, then attempt to make it back to land.  Only bail out once the engine actually stops running and if insufficient glide range to put down.  It's really worth getting over (or at least nearer to) land before parachuting out anyway, as that increases the chance of saving the aircrew.

And in the heat of a crisis, the training can be forgotten or disregarded.  Lots of "heroic" acts in wartime fall into that class!

You could also pour a cup of carborundum polishing grit into the induction air inlet. This will get sucked up into the engine and quickly ruin it. This trick was used by air racers in the 1930's to sabotage their competitors' airplanes.

That would likely occur during or shortly after engine start - so still save on the ground and unlikely to get the injuries the author needs for his story.

@tsg Yeah, `30's air racer saboteurs weren't trying to kill each other for the most part, just prevent their competitors from flying in the first place.

The hard part is circumventing the pre-flight checks.
You could locate the ammunition belt for the 4x 20mm Hispano cannons and cram in a dodgy round that will just plain explode when the firing mechanism hits that round.
The Hurricane would climb to intercept and once lined up would fire its cannons and start a fire as the false round explodes, detonating a few around it as well.
One could say its wing members would assume some defensive weapons on the bombers / other fighters achieved a critical hit.

Hispano cannons were fed from a drum magazine.  I don't think there's anything flammable near by,  the pilot has a parachute, why not use it?

Drum is even better for sabotage if you are part of the ammo handling ground crew. Place a dodgy round in the ammo (belt) and feed the drum magazine. Now the dodgy round is hidden within the drum. Any subsequent inspection will only see a drum magazine that has been correctly installed into its space.

A cup of sugar in the fuel is a fairly traditional way to go, and was recommended by contemporary sabotage manuals.
As @Milwrdfan pointed out in comments though, "sabotage" covers a range of outcomes.

Maim but not kill, that's a fine line to walk
So, you're forcing him to land an unflyable plane. You need some sort of sabotage that takes effect before the plane reaches parachute height.
A bomb or mechanical control-wire cutter activated by raising the the landing gear perhaps.
the aileron wire however seems to be is quite far aft of the wheel bay and you'd probably need to loose both and possibly the rudder also to render the aircraft unable to climb or land safely.
Some sort of engine or fuel sabotage seems better, but again timing is an issue
the fuel tanks are in the cockpit but are self-sealing so it'll quite a lot to make a large enough hole to leak (possibly some sort of hollow lance would work?)  the landing geat closes near the forward tank which is convenient for a trigger, but this all seems very complicated
A small explosive wited to one of the indicators on the control panel could burst the forward fuel tank filling the cockpit with fire
With the bomb triggered before takeoff and the pilot suffers burns, if immediartly after takeoff . burns and a crash-landing, or during flight. burns and a possibly bad parachute landing.

You need the plane to crashland, but not crash fully. So crippling not destroying the plane.
It is launching from Malta, but you want a land landing, not water landing? Thus a failure in the air, within 5 minutes of takeoff (better 2 minutes), as Malta is tiny and surrounded by much ocean.
Sabotage the coolant system
Just put a glass vial of nitric acid in the coolant air intake(closing the radiator intake flap again).
The actual amount of time needed with the plane is less than 2 minutes, and no suspicious hacksawing away at the plane, just one entry into cockpit, open the vent, put in the vial, close the vent again. Routine maintenance. (It does require careful prep, of course, but the materiel is not scarce or even suspicious, it's used in the repair bay)
Cycling the radiator flap is not part of the takeoff prep. The flap is kept closed until the coolant temp is up to the correct levels, which requires about 2 minutes of flying power. When the flap is opened, air rush will smash the vial, spilling nitric acid over the radiator grid. About 30 seconds later, the radiator fails catastrophically. The plane is still low and climbing, and about 5 minutes from the airstrip.
You now have a plane with a faltering, soon dead engine.
Smoke pouring into the cockpit from glycol spilling everywhere.
Poor visibility, but enough for the pilot to think he can make it back to the airfield. He doesn't, of course. At least not gracefully. Post-crash fire easily hides the evidence of sabotage.

Perhaps one could subtly trim, or add weight to a propeller blade in a way that wouldn't be easily seen by eye.
The original Hawker Hurricane propeller was made of wood (perhaps later ones were as well  I don't know), and tools such as wood drills and fillers existed and were available to good quality.
So let's say you get access to the hanger, or a spare prop.  You drill a hole in a blade, insert a lead rod, and seal with some nice filler, then tint and coat it, so it doesn't show to the eye. Its not something you really look for or test anyway. Or you shave some thickness away, and coat it.
Then if you did this at home, you sneak in and swap propeller blades either at night or by faking being authorised to be there.
Now let's think what happens if you do this. The prop behaves perfectly on the ground. It spins when pushed, works just fine. The engine starts up and its probably still just fine. A bit noisy maybe, not a problem.
But at takeoff and flying speed, its now no longer balanced. Every turn it makes, its off balance weightwise and shaking the prop shaft and engine, its mounts, and putting great mechanical strain on it - and think how fast those props turned in heavy use. The propeller pivot is wood too, and not that robust against such excessive vibration and strains either - and has a hole in one blade which isn't great either.  The pilot won't hear anything, because headset and cockpit, and will at most feel the plane is shaking or a bit odd. I'm not sure what they'd notice.
After a little while of high speed rotating, dependent on how off balance it became, the mounts or the prop itself will suffer from fatigue, loosened fixings, or unexpected strain, and fail midair during some climb or dive, or perhaps even straight flight.
(The Americans and Israelis got the Iranian uranium centrifuges the same kind of way, with Stuxnet, so "making it shake itself until it breaks" is a proven time delayed sabotage technique, in a way.)
The one place this won't happen, is during pre flight testing......

Not really.  When the plane is in the air, a pilot will throttle back to save fuel, at least until they get into a dogfight.  But the one time every plane runs at 100% thrust is at takeoff - and takeoff starts on the ground. :)  The pilot is guaranteed to feel that kind of vibration.  You can virtually guarantee the pilot would abort their takeoff run with their wheels barely leaving the ground.  At the very most, they would circle back round and land immediately, seconds after taking off.  There is no chance at all they'd leave the airfield.

@Graham An experienced pilot would notice this immediately, but a fresh, recently and hastily trained pilot might miss it?  We're talking WWII, when lots of pilots were being very quickly trained, so there's a good chance you have a new pilot who doesn't recognize the signs yet...

The Hurricane's Merlin engine was designed to handle a huge prop imbalance, and still keep running for a few minutes. A bullethole in the prop did not even prevent combat flying. A larger hole or gash would incapacitate the pilot by vibration, before it stopped the engine system from working. And the moment the pilot feels bad vibration, he would throttle down. 1/2 the RPM would deliver 1/8th the vibration energy, and still allow a return to base.

I would think probably the best way to sabotage an airplane to virtually guarantee the aircrew is killed if they cannot bail out would be to damage the control cables or bellcranks for elevator and elevator trim, causing a nose down trim condition with no means to effectively recover.  This would be difficult to conceal, and once discovered, would quickly be tracked down to the individual(s) last working on the aircraft, but a savy mechanic might be able to do this in a remote section of the fuselage not likely to be seen or inspected during a preflight.
Another possible method is to put diesel fuel in the fuel tanks as opposed to aviation gasoline. The engine won’t be able to burn it and the pilot will lose power very quickly. This still leaves a possibility for force landing as opposed to the answer above.

Part of the standard preflight procedure is to check the controls and control surfaces to make sure they move properly; part of the takeoff procedure is to lift the nose.  If the airplane is permanently trimmed nose-down, this will be obvious during preflight, or if preflight is skipped, it will be obvious when the airplane refuses to take off.

You may be able to damage the system enough that a preflight check is possible, but it will fail once its subject to aerodynamic loads.

Who downvoted this answer?  Really?  C'mon...

Cross-rig the trim controls.  So when trying to correct say, nose-down, the 'correction' has the opposite effect.  Not a guaranteed fail but quite possibly cause a pilot to conclude the plane is uncontrollable and bail out.
(RAF bases on Malta were very pressurised both physically and psychologically.  When writing, make sure there is nothing casual about your ne'er-do-well.)


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Lost Logbook, but have all flight information on ZuluLog
Good afternoon everyone.
Back in 2013 / 2014 I did Part 61 training in WA State. I had to stop due to financial difficulties at that time.
I moved to Phoenix 6 years ago, and now that I want to get back in to finishing up, discovered my Logbook is nowhere to be found.
I have always been smart enough to log in to ZuluLog and record my time for that flight, what we did, airports we went to, etc.
I contacted the school in WA State, and my flight records are before they went to FSP for their scheduling. I was told they "should" be available in their Loft, and someone would have to go research. I am still waiting since I contacted them 05-NOV-21 for even a response to my email. Whenever I call, I always get someone else who says they know nothing about it, have never seen an email, etc. etc. Even the instructors I did my schooling with are no longer with that place, and it has been sold / bought three different times since my last flight.
My question is this... Since I have everything saved in ZuluLog, is there any way to use that to incorporate a new logbook? I have done a couple flights out here in Phoenix to try and get a feel for a school I want to continue on with.
I've got 50+ hours from my previous training that I just don't want to lose and have to start over unless I absolutely have to.
I appreciate the info and direction anyone can give.
Have a great day, and stay safe up there!

I am not a pilot and know very little about the regulations regarding pilot training. But looking at ZuluLog's website, it seems like they are a logbook and (it would appear to me) you could use them only, without ever writing down anything in a paper logbook, and it would be perfectly legal. Do you have any reason to doubt this is the case?

We already have a question on replacing a lost logbook, although I'm assuming your main concern is how/if to use the information in ZuluLog to rebuild your paper logbook.
The key point here is that ZuluLog is a logbook (it even says so on their website). The FAA doesn't say anything about how or where you maintain your logbook, and an electronic one is completely fine to use and very common. So if all your time is recorded in it then you haven't lost anything. My advice is to continue to use ZuluLog or another electronic logbook as your primary one. It makes everything much easier with tracking and reporting hours and other details for checkrides, insurance, flying clubs, currency etc. Most online logbooks allow your instructor to do electronic endorsements too.
Having said that, I guess there were handwritten instructor endorsements in your paper logbook to record your training and it sounds like there's no easy way to track down the instructor(s). Realistically, after 8-9 years that probably doesn't matter much because you'll be starting more or less from scratch with a new instructor anyway.
A lot of logging is effectively on the honor system because there's no objective way to validate it. If the hours in ZuluLog do end up being necessary for your checkride it seems to me like a simple explanation to the DPE and they're unlikely to challenge you on it. If it bothers you, you could consider adding a comment to ZuluLog stating that "training flights and endorsements prior to MM/DD/YYYY were recorded in a paper logbook that was lost in YYYY". You could even write and sign that on paper, then take a photo and upload it to ZuluLog (I assume; I don't know how it works), as a kind of formal statement/record of events.

Yes sir, that was the synopsis of my question. I have every single minute I flew in Zululog. Tail #, CGI I flew with, etc. Only issue is no endorsement, so I didn't know if it was usable or not. Here in AZ, I have only found a couple CFI's that know what the hell Zululog is. The 1st school I went to get a feel for, didn't even know what BasicMed is., and my Zululog was not acceptable, I would have to start over from scratch with them. Seems that doing schooling in Class G Airspace, the CFI's are a bit more knowledgeable. Either that, or it's just the young 20'ish CFI's nowadays. LOL

Hello - I'm the founder of Zipwire which I built to journal my work as a freelance software engineer. I'm interested in using the blockchain to track my time and have my boss endorse it using a blockchain thing called an "attestation". It sounds like exactly what's needed for aviation, right? You'd never be able to lose your record, and the endorser could themselves be endorsed in a chain, up to an authority. Is this interesting to folks??


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If, one day, we have an electric airplane, will it be easier to control than a fuelled airplane?
Elon Musk said that Tesla will make battery which can last for million miles.  So probably in the next few years there will be a (small) airplane powered by an electric motor rather than by fuel.
If this happens, will controlling the electric airplane be easier?  The CG won't shift as fuel is consumed.  But the constant battery weight probably will problem to the maximum landing.

Just to clarify in case you misunderstood: The life expectancy of the battery will be a million miles. It will not be on a single charge, rather you can expect the battery hold itself for many charge cycles

The first paragraph of the question is not relevant to the question nor is the relation between control and landing weight. In essence the question is viable, electrification allows designers to place motors virtually everywhere on the plane, this can aid in differential propulsion control. You should update the question!

The question should be rephrase so seem less speculative. Something like "how difference in engine placement enabled by electric propulsion can affect manoeuvrability?" would be more specific, obviously not speculative and would cover a large part of the question.

I think the underlying question is a good one, even if it is masked a bit by the confusion over Tesla comments.

Differential thrust will be more precise, responsive and efficient, so is air(engine) breaking. But conventional layout doesn't benefit from this much, except like V22 or a helicopter.

A good explanation about electric planes.

There are a few electric aircraft now, and because batteries hold far less energy than fuel, they're low-performance and short-range compared to normal aircraft.
If we imagine that at some point in the future we'll have batteries that can match fuel, the answer would be: Only slightly.
Back in the 60's and 70's, airliners regularly carried a flight engineer, who's full-time job was to monitor the engines and tweak various controls to keep them running properly. Now that's almost entirely automated. Pilots still have a checklist to follow to start the engines, and things to monitor during the flight, but it's a small part of their responsibilities.
Even if switching to electric propulsion completely removes this, it won't make a huge difference to the pilot. (and that's assuming that the electric system has nothing to monitor or adjust)
The aircraft handling is unlikely to be affected significantly, although there are be minor effects:

Fuel gets used up, so electric planes will have to be designed with stronger landing gear.
Electric motors are easier to scale, so it's easier for small aircraft to have multiple, counter-rotating motors to eliminate torque swing.
The battery is the heaviest part of an electric power system (and for one with hours of endurance, by an order of magnitude), so fitting a motor with excess power has a relatively smaller weight penalty. Electric power systems are good for providing short bursts of high power between long periods of cruising. Unfortunately this is more useful for a car than an aeroplane.
It would be much easier to design an electric power system for an aerobatic plane. Supplying fuel and lubrication while flicking between positive and negative G takes careful design.
Electric motors are quiet, but they are still transferring lots of power into the air, which is inherently noisy.

Ultimately these are all minor effects compared to the elephant in the room, which is that batteries are far heavier than fuel.

Actually, your point about battery-powered aerobatic aircraft is a good one. While I'm sure that liquid fueled aerobatic aircraft are currently designed with fairly small fuel tanks located as closely as possible to the CoG to eliminate CoG shifts throwing things out of whack for the pilot while performing extreme maneuvers, having batteries as a solid, non-shifting "fuel" source will completely eliminate any CoG changes no, matter how small, from being points of concern.

@FreeMan  the problem is not so much the CG change, as that a liquid fuel sloshes around and sometimes the intake pipe sucks up air instead of fuel. And famously, the Spitfire's carburettor float-bowl cut the engine during negative G, while the Me-109's fuel injected engine was fine.

Isn't the landing gear dimensioned for an emergency landing with full tanks?

Nice info. I was surprised by the facts that will be many restriction and limitation by the electric airplane. Not as what was on my mind.

@Orbit - for most airliners, max landing weight is lower than max take-off weight, and they'll dump fuel if they have time. They can land at max weight in an emergency, but it'll damage the tyres and brakes, and can over-stress the airframe - but that's acceptable if (for example) an engine is on fire. https://aviation.stackexchange.com/questions/2854/when-are-aircraft-required-to-dump-fuel-for-emergency-landings/2855#2855

Robin makes a lot of great points, but since we are talking on a purely hypothetical case lets have fun and take it to supersonic speeds.
Let's assume that somehow batteries have the required energy density to be used to run some sort of low-bypass electric turbofan to propel our aircraft to high speeds where the neutral point of the aircraft starts shifting aft on typical configurations. Additionally, since batteries do not change weight as energy is depleted, the CG stays at the same place so the static margin of the aircraft would start to increase on a statically stable aircraft as the distance in between the CG and NP increases. Hence, either the control surfaces must be sized to ensure controllability through the whole flight envelope (low speeds and high speeds), or another system must be developed to ensure that the aircraft remains controllable. The Concorde and the TU-144 used a fuel transfer system to move fuel from the center section of the aircraft to containers located in the back, as to shift the CG aft proportionally to the NP movement. Theoretically, an electric airplane could shift its battery storage, but batteries have a pre-established shape, so shifting that mass may be difficult. Also, sizing the control surfaces for high speeds, rather than slow speeds (as is usually the case), could create extra aerodynamic forces that would create extra drag and/or extra stresses being put on the body.
One solution could be to make the aircraft unstable at low speeds, and as the neutral point moves past the CG at very high speeds the aircraft would then become stable. But this would increase the complexity of flight and an advanced controls system would be necessary.
I can't wait for the day that batteries have the energy density required to propel aircraft past the speed of sound, but for the stability and control people there will be a lot of challenges lol.

Don't hold your breath @Michael Ibanez, the day of supersonic battery powered passenger flight will most likely not be seen by us. Current batteries can deliver approx 500Wh/kg, to match the energy density of kerosene, batteries will have to become about 20 times more efficient. By engineering standards, that's ridiculously much :)


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Runway edge and center line lights spacing
We use the number of visible lights on a runway edge/center line to estimate the RVR in LVTOs. So, what is the minimum/maximum spacing between runway edge and center line spacing ?
Where do we find this information if published on Jeppessen charts ?
If possible to have more details about such standards.

This is better than what I would have answered.  https://www.boldmethod.com/learn-to-fly/regulations/what-to-know-about-runway-lighting-space-and-color-configuration-explained/

Thank you for your contribution, I've read that article but it doesn't mention if those spacing are published on Jeppessen charts.

You don't actually mean to ask for the spacing "between runway edge and center line," the runway half-width, right?

@CamilleGoudeseune -- as far as I can tell, that is what he or she is asking about

I am actually asking about the spacing between each light bulb on the runway centerline and edges

The FAA AIM 2-1-5 says:

Runway centerline lights ... are spaced at 50-foot intervals.

(The previous section, 2-1-4, describes runway edge lights, but mentions nothing about their spacing.)
Figure 3 of the FAA's AC 150/5340-30D and page 4 of AC 150/5340-30H say that runway edge lights are at most 200 feet apart, and uniformly spaced except for intersections.  No minimum spacing is specified.

Only some of the examples I found of Jeppesen charts with an "Additional Runway Information" section mentioned lighting therein;  none mentioned the spacing of edge lights.
Jeppesen might not even ask airports for that detail.  If you need to know that for just a few airports instead of thousands, either ask the airports yourself, or look at aerial photos.  For the airports near me, for instance, a few seconds' zooming and squinting in Google Maps showed me that C16 Frasca Field's are about 180 feet apart, KTIP Rantoul 200 feet, KCMI Champaign 200 feet.
Maybe only tiny airports like Frasca have spacing closer the mandated 200 feet, just to minimize the cost of purchase and maintenance.  If so, that's another reason Jeppesen would exclude that from its charts.

Thank you for the detailed articles, they answer 90% of my question. Do you know if the information about the spacing is published on Jeppessen charts ?


text:
What are the difficulties in building transonic airliners?
If the sonic boom is an issue, why don't we build airliners that are capable of flying just below Mach 1? Big airliners fly at Mach 0.85 at most, and the record for current sub-/transonic civilian aircraft is the Cessna Citation X+'s Mach 0.935. Why don't we build airliners that cruise at Mach 0.95? Also, what would happen if the Citation X+ tried to reach or surpass Mach 1, since it's anyway close? There it isn't answered.

Related: https://aviation.stackexchange.com/questions/11936/are-we-at-peak-speed-efficiency-for-jet-airliners-at-mach-0-85

Welcome to aviation.SE! We have several closely related questions, do any of them help you? Here, here.

That is because as you approach the transonic regime, the drag on the airframe begins to rise and can reach up to ten times the subsonic drag. after you go supersonic, the drag falls down again- and this makes the transonic regime the worst place to operate a plane from a fuel burn standpoint. So you either stay subsonic, operating below the drag rise point, or supersonic, comfortably beyond that point.
Another consideration is this: Even if you are subsonic but nearly supersonic, there will be points on the airframe where the airflow is locally supersonic. You can actually see this in Boeing's long-distance planes, where a cabin seat at roughly mid-chord affords you a view out the window of the normal shock sticking up from the wing at high-speed cruise. If the flow goes supersonic at one of the control surfaces, it may upset the controllability of the plane, which would be undesirable- so better to stay comfortably out of the transonic regime for cruise.


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What are those flight level values on an airway?
I have downloaded from this link the chart of available airways over the Canary Islands. There, in some of the airways, it says
FL660
FL145

As far as I know, these two numbers are the maximum and minimum values of the flight level which can be used while traversing said airway. However, I haven't found any online document which can be used as a source to verify if I am right or not. Can someone please indicate where I can read about chart interpretation?